Increased synthesis of an Escherichia coli membrane protein suppresses F exclusion of bacteriophage T7

Increased synthesis of the protein FxsA alleviates the exclusion of T7 in c ells harboring the F plasmid. In contrast to wild-type or cells defective i n fxsA, overexpression of fxsA(+) allows T7 to form plaques at normal effic iency even though the burst size is reduced to about half that obtained on the isogenic F- strain. No defect in DNA synthesis was observed but late pr otein synthesis remains partially inhibited and a reduced level of cell lea kiness, a prominent feature of F+ cells abortively infected by T7, persists . The FxsA protein is shown to be a cytoplasmic membrane protein. How T7 av oids exclusion by F in cells that exhibit increased levels of FxsA is discu ssed in terms of its membrane localization. (C) 1999 Academic Press.